Agitator



Juhe 17, 1969 A. SZEGVARI AGITATOR SZEGVARI Sheet INVENTOR. ANDREWOriginal Filed March 5, 1964 ATTORNEY June 17,1969 A. SZEGVARI 3,450,355

AGITATOR Original Filed March 5, 1964 Sheet 2 of 4 INVENTOR. ANDREWSZEGVARI ATTORNEY June 17, 1969 A. SZEGVARI 3,450,356

AGITATOR Original Filed March 5, 1964 FIG. 5

FIG. 6

E ZONE 3 /ZONE 2 ZONEYI I j n L I zone: [ZONE 2 zone 3 INVENTOR. vANDREW SZEGVARI nymc d ATTORNEY Original Filed March a, 1964 Y June 17,1969 1 AGITATOR Sheet 4 014 FIGIO INVENTOR. ANDREW SZEGVARI ATTORNEY A.SZEGVARI I 3,450,356

United States Patent US. Cl. 241-172 13 Claims ABSTRACT OF THEDISCLOSURE Grinding apparatus which comprises a vessel partially filledwith spherical grinding elements, and a central vertical agitator withsupports extending different distances therefrom and each provided witha terminal activator.

This is a continuation of my application Ser. No. 349,550, filed Mar. 5,1964, and now abandoned.

This invention relates to an agitator for spherical attrition elementsin a vessel in which a material suspended in liquid is ground fine bythe action of the activated attrition elements; and it includes themethod of agitation.

The spherical attrition elements are mechanically acted upon byrevolving agitating means, and this patent appli cation discloses how tomake this agitator means more effective and how to affect the agitatorconstruction to bring about uniform kinetic activation of the grindingmedia in the matrix thereof throughout the grinding vessel.

Kinetic activation of an attrition aggregate is described in US. PatentNo. 2,764,359, according towhich an agitating device impartscontinuously sufficient mechanical energy to a large enough number ofattrition elements, so that a random distribution of the momenta coupledwith an incipient free path develops and these activated elements arekept out of static contact with one another.

The general difiiculty in obtaining kinetic activation encountered (whenusing a revolving agitator is a tendency to cause circular groupmovement of the attrition ele ment aggregates whereby the whole systemis moved like a coherent solid mass; while kinetic activation occursonly when the adjoining attrition elements meet, having a differingvector of motion. In addition, this has to be brought about with minimumaxial circulation of the attrition elements as described in my UnitedStates patent application Ser. No. 65,796 filed Oct. 28, 1960 (now US.3,149,789).

Another difiiculty when generating kinetic activation with agitatorscommonly used in industry and described in literature is that the actionis not uniform, and extends primarily around a peripheral zone of theoutermost extension of the agitators. Most of the kinetic activationtakes place around the end of an agitator bar, and decreases to zero asone approaches the central shaft along the agitator bar.

It is easily seen that the activating means of the agitator movingthrough an aggregate system causes most kinetic activation if thevelocity gradient in the contacting aggregate system is largest, inother words, the average velocity within this aggregate system ischanging fastest from point to point. The largest velocity gradient isobtained at a terminal portion of an agitating means that extends at aright angle to its support and at a right angle to the plane of rotationinto the aggregate system. Such a means is herein called an activator.

In order to provide activation throughout the entire cross section ofthe system of attrition aggregates, activators are placed on supportmeans so as to locate them Patented June 17, 1969 at a certain distancefrom the axis of the agitator; and in large vessels activators arelocated on them in several radii. The activators located nearer the axisof the agitator are larger than those located farther away in order toproduce the same kinetic activation of the attrition elements when theactivators are moved through them.

It is important that these activators should move through a path of theaggregate system which is otherwise not acted upon in order to decreasethe group movement of the entire aggregate system. Therefore, theactivators in their circular path should be as far apart from each otheras practical, and preferably there should be only one activator in eachcircular path, except in a very large vessel. Further, the paths of anactivator or other agitator means should be as far as possible away fromall other agitator means, like other activators or activator supports.

If the volume of the vessel is divided into several concentric agitatorzones the liquid preferably rises up through the vessel with nointermixing of the material from these various zones.

To provide uniform kinetic activation throughout the entire contents ofthe vessel, it is necessary to provide equal or nearly equal activationin each zone, and to distribute the activators so as to obtainsubstantially equal kinetic activation at each level in each zone.

The means for providing activation in each zone may take any one ofseveral forms. It is proposed in this application to use radial supportsarranged at angles to one another around a central agitator shaft, or toattach additional terminal structures to axial supports spaced atdifferent distances from the agitator shaft to serve as activators ofthe grinding media.

The invention is further described in connection with the accompanyingdrawings.

Several specific embodiments of the invention are shown in the drawings,in which:

FIGURE 1 is an elevation in section showing an agitator with agitatorbars or rods extending generally axially of the shaft and activatorsattached thereto, in a tapering vessel;

FIGURE 2 is a detail of the bottom of the same, at right angles to theview shown in FIGURE 1, showing scoops at the bottom of the agitator;

FIGURE 3 is a horizontal section on the line 33 of FIGURE 1;

FIGURE 4 is an elevation in section of an agitator with horizontal armsand activators attached thereto, in a small cylindrical vessel;

FIGURE 5 is a section on the line 5-5 of FIGURE 4;

FIGURE 6 is a plan view of an agitator arm with two activators attachedthereto designed for use in a vessel of larger diameter;

FIGURE 7 is an elevation of the same;

IGURE 8 is the same as FIGURE 7, except that the shaft is shown partlyin. section, and zones of activation are indicated;

FIGURE 9 is an end view of the agitator arm of FIG- URE 7 on the line 99thereof;

FIGURE 10 is an elevation in section showing part of the top of amodified type of agitator; and

FIGURE 11 is a plan view on the line 1111 of FIG- URE 10.

FIGURE 1 indicates that when in operation the attrition elements 1 coverthe top of the effective portion of the agitator 2, and may be retainedin the vessel 3 by a screen 4.

The agitator 2. shown in FIGURES 1 to 3 includes two scoops 5 at itsbottom spaced from the bottom of the vessel a distance of about threetimes the diameter of one of the attrition elements. These lift theattrition elements 1 off the bottom of the vessel 3 when the agitator 2is put in motion. Scoops may be omitted.

The agitator comprises a central shaft 6 having activator supports 7extending in the general axial direction of the shaft and attachedthereto by means of radial arms 8 as shown in FIGURES 1 to 3. Activators10 are attached to the activator supports 7.

As the liquid flows upthrough the vessel, the least agitated flow isclose to the vertical shaft 6, the kinetic activation being much lessthere than near the wall of the vessel 3. If the axial activatorsupports 7 are located at different distances from the shaft 6 of theagitator as illustrated in FIGURES 1 to 4, the activators 10 may belocated on only the inner supports instead of on all the supports asthere shown.

The agitator of FIGURES 4 and is shown in a cylindrical vessel 20. Theactivator supports 21 are all of the same length but are so positionedin the holes 22 that one end of each to which an activator 23 isattached projects from the shaft only about half as far as the otherend. The support ends are located farther from the shaft than theactivators 23 so as to produce substantially uniform agitation over thewhole area of the vessel, and the activators 23 are distributed over thearea to accomplish this end.

FIGURES 6 to 9 illustrate a structure for use in vessels of largerdiameter in which there are a plurality of activators on each support29. There are many supports in each agitator extending from the shaft 30in different directions, although only one such support is shown in eachof these figures. The support extends through the shaft and is held inplace by the pin 32. The configuration would be similar to that shown inFIGURE 4 for a vessel of smaller diameter. The dotted lines indicatethree cylindrical zones of activation, numbered 1, 2 and 3, ofprogressively greater diameters. There may be a larger or smaller numberof zones in each of which activator means is located. When the agitatoris rotated the activator 31 provides activation in zone No. 1 nearestthe shaft. Activator 33 in zone No. 2 is somewhat smaller. The end ofthe support 34 acts as an activator in zone No. 3. The activator 33 inthe intermediate zone is intermediate in its capacity of activationbetween the activator 31 and the support end 34.

In FIGURE 8 the areas adjacent the different activating means are shadedto indicate the areas of intense agitation immediately adjacent each. Anarea of somewhat less agitation is indicated as surrounding each of theshaded areas. The different shaded areas overlap as the agitator isrotated.

The leading edge of each support of the agitators shown in the foregoingfigures tapers to a knife edge so that there is minimum group rotationof the attrition elements as a mass. (See particularly the end andsectional views of supports 7 in FIGURE 3 and the end view in FIGURE 4.)Kinetic activation is increased as rotational movement of the aggregatesystem as a whole is minimized.

T he agitator of FIGURES and 11 utilizes flat plates 40 for activatorsupports which cut through the bed of attrition elements with minimummovement of them as a whole and minimum displacement, one from another.The plates are spaced radially of the shaft 41 to locate the activators42, 43 on all sides of the shaft, and they are spaced axially of theshaft so that no two activators move in the same annular zone about theshaft. Alternate activators 42 and 43 are spaced different distancesfrom the shaft so as to kinetically activate the attrition elements inzones spaced different distances from the shaft. Thus, the activatorsare so located as to most efficiently effect kinetic activation of theattrition elements throughout the whole of the vessel in which theagitator is located.

The invention is covered in the claims which follow.

I claim:

1. Apparatus for fine grinding which includes a vessel with an agitatorand spherical grinding elements therein in such quantity as to partiallyfill the vessel about the bottom of the agitator, the agitatorcomprising a central 4 vertical shaft with supports radiating therefromand individual terminal activators attached to the separate supports andso exposed thereon that each activator generates a path different fromthat generated by the support to which it is attached when the agitatoris rotated about its vertical axis.

2. The apparatus of claim 1 in which the activators are attached to thesupports at different distances from the shaft and so exposed thereonthat when the agitator is rotated grinding elements located at alldistances from the central shaft are agitated.

3. The apparatus of claim 1 in which the frontal elevation of eachsupport is less than the frontal elevation of the one or more activatorsfastened thereto so that the supports cause substantially no drivingaction in the medium in which the agitator is located when the agitatoris rotated about the vertical shaft.

4. The apparatus of claim 1 in which the supports are relatively thincompared to their width and and are flat in horizontal planes andsubstantially perpendicular to the central shaft and extend outwardlyfrom only a small portion of the shaft circumference and each have atleast one activator extending perpendicularly therefrom.

5. Apparatus for fine grinding which includes a vessel with an agitatorand spherical grinding elements therein in such quantity as to partiallyfill the vessel about the bottom of the agitator, the agitatorcomprising a central vertical shaft with linear supports spaced from theshaft and extending lengthwise of the shaft, with activators protrudingfrom the supports at spaced intervals.

6. The apparatus of claim 1 in which the activators are distinct fromone another and supported by the shaft at different radial distancesfrom the shaft.

7. A bed of grinding media in a grinding vessel, and extending down intosaid bed an agitator with an axis of rotation and equipped withactivators on supports at different distances from said axis, theactivators with the smaller radial distances from the axis being largerthan the activators at the larger radial distances, the relative size ofeach activator being varied inversely with the radial distance.

8. The combination of claim 7 which includes a central vertical shaft,supports extending substantially perpendicularly therefrom, andactivators of different activating capacities on the supports andextending generally axially of the shaft.

9. An activatable bed of grinding media in a grinding vessel, andextending down into said bed an agitator which includes openings throughthe shaft in various directions and a support in each opening whichextends from each side of the shaft, with at least one activatorextending away from each support on each side of the shaft in adirection generally perpendicular thereto.

10. Apparatus for fine grinding which includes a vessel with an agitatorand spherical grinding elements therein in such quantity as to partiallyfill the vessel around the bottom of the agitator, the agitatorcomprising a central vertical shaft with supports attached thereto andactivators of different sizes attached to the supports at differentdistances from the central shaft, with the vertical cross-sectional areaof each activator perpendicular to a line radiating from the centralshaft, varying inversely with the radial distance between it and thecentral shaft.

11. Apparatus for fine grinding which includes a vessel with an agitatorand spherical grinding elements therein in such quantity as to partiallyfill the vessel around the bottom of the agitator, the agitatorcomprising a central vertical shaft with supports attached thereto andactivators attached to the supports, with the supports each extendingthrough an opening in the central shaft and at least one activatorextending away from each support on each side of the shaft in adirection generally perpendicular to the support.

12. Apparatus for fine grinding which includes a ves sel with anagitator and substantially spherical grinding 5 elements therein in suchquantity as to partially fill the vessel about the bottom of theagitator, which agitator comprises a central shaft with elements of theagitator extending perpendicularly outward from the shaft and extendingdifferent distances away from the shaft on opposite sides of the shaft.

13. Apparatus for fine grinding which includes a vessel with an agitatorand substantially spherical grinding elements therein in such quantityas to partially fill the vessel about the bottom of the agitator, whichagitator cornprises a central shaft with elements extendingperpendicularly outward from the shaft which are positionedasymmetrically with respect to the center of the shaft.

6 References Cited UNITED STATES PATENTS GERALD A. DOST, PrimaryExaminer.

US. Cl. X.R.

